Juno's Loud

DmitryK · Post by **DmitryK** » Thu Oct 05, 2006 8:22 am

Hi everyone.

Bought a Juno off eBay for cheap, and the seller did state that a voice chip was dead. I bought one off eBay as well, and am poking around the PCB and in the test mode.

Now, there is one thing I noticed, and that is that one of the voices sounds much louder than the others. It's not distorted, not at the volume I'm playing at, but adjusting the gain on the PCB doesn't solve the problem.

Could this be another faulty voice chip, or is there something I can do?

Thanks in advance!

Post by **Maschinengeist** » Thu Oct 05, 2006 6:45 pm

Right now, I wouldn't know what to answer.

I think minime123 is more qualified than I to answer this. But I'll look up for a possible solution as time permits.

Bitexion · Post by **Bitexion** » Thu Oct 05, 2006 11:14 pm

Try sending a PM to minime123, he seems to have repaired all kinds of vintage synths.

Post by **Maschinengeist** » Fri Oct 06, 2006 12:13 am

You adjusted these, right?

I've got the Juno-106 service manual, which can come in handy. If you got some (see my website for the needed ones), we can trade.

dougt · Post by **dougt** » Fri Oct 06, 2006 1:08 am

The Juno-106 Service Manual is on-line here -

http://www.hinzen.de/midi/juno-106/manual/juno-serv.pdf

It could also be the filter cutoff freq for that voice being higher than the rest making it seem louder. The trimmers for filter freq are VRs 28, 24, 19, 14, 9, and 4 (voices 1,2,3,4,5,6). Also, if the VCA Level trimmer for the louder voice doesn't seem to do anything it could be a bad trimmer pot. I've seen them fail before.

Post by **Maschinengeist** » Fri Oct 06, 2006 1:31 am

That should help

DmitryK · Post by **DmitryK** » Sat Oct 07, 2006 3:59 am

Hi,

Thanks a lot for the replies!

Yeah, I've made the adjustments shown on the picture (I've found the exact same image actually). In fact, I think I've made adjustments to everything that could be adjusted, and surely will have to calibrate the Juno later on, but right now I'm concerned with the loudness of the chip.

I've contacted D' Naab, the guy who makes replacement chips for the Juno, and he said it indeed could be the chip.

Now, I've got one good one off eBay, and I thought that instead of replacing the dead one, I should first try to take out the loud chip, and put the good one in place of it. If the volume normalizes, then the original one is toast.

One question though - is there any dependancy among all 6 voice chips? I.e. could it be that the #5 (loud) chip is behaving this way because of the other dead one?

Thanks again for the replies!

dougt · Post by **dougt** » Sat Oct 07, 2006 9:16 am

One thing I've done before that will make it a lot easier to troubleshoot is to install sockets where the bad (or suspect) chips were so you can plug in the chips quick and easy... You can take a normal 24-pin DIP socket and cut it to get 2 SIP sockets...

Also can you tell me if adjusting the VCA Level trimmer for the loud voice does anything? Can you make it quieter to match the other voices?

DmitryK · Post by **DmitryK** » Sat Oct 07, 2006 10:04 am

dougt wrote:One thing I've done before that will make it a lot easier to troubleshoot is to install sockets where the bad (or suspect) chips were so you can plug in the chips quick and easy... You can take a normal 24-pin DIP socket and cut it to get 2 SIP sockets...

Also can you tell me if adjusting the VCA Level trimmer for the loud voice does anything? Can you make it quieter to match the other voices?

It'd be nice to install sockets, as it seems I may have to install more in the future, and I really like the sounds I've been able to get out of the Juno so far.

As to the VCA trimmer, it hardly helps. I turn it all the way down counterclockwise, and the change in volume is minimal. I'm quite certain it's not supposed to be drastic anyway.

One way I was able to equalize the volume is by boosting the resonance of the VCF, and turning cutoff about halfway up. The sound seems to loose a lot of lows, and the VCF starts functioning like a high pass filter almost. It's definitely no way to fix the problem, as it just masks it temporarily, but that did make me wonder if it's just an adjustment of some sort, because the voice sounds fine. It's just too loud, that's all.

Thanks for the replies!

Bitexion · Post by **Bitexion** » Sat Oct 07, 2006 1:39 pm

Just wondering, are these chips inserted into a socket, or must you solder them to the PCB? The voice/filter chips I mean.
If one breaks, is it as simple as taking it out of the socket and pushing the new one in?

dougt · Post by **dougt** » Sat Oct 07, 2006 9:15 pm

They are soldered in that is why I suggested installing sockets.

DmitryK · Post by **DmitryK** » Sat Oct 07, 2006 9:19 pm

dougt wrote:They are soldered in that is why I suggested installing sockets.

That's right

.

This Juno has not been repaired once. In fact, I don't think it was ever cleaned since the day it was made. I felt a mutual understanding when I was cleaning dust from the inside. I'm sure Juno felt thankful. Now I want to get her up and running like in her good days

DmitryK · Post by **DmitryK** » Sun Oct 08, 2006 4:25 am

I've ordered one more chip for the Juno. Even if all but one are good on my Juno, something tells me one more may fail at some point later on, and I like the sounds too much to not be able to use the synth in the future.

As to the sockets, it would indeed make sense to cut a DIP one in half. Not sure that would save any money vs. an SIP socket, if there are any on the market. I'm still learning as far as repairing electronics goes, but I've spent quite a bit of time soldering as a kid, and it's probably a good skill to have if you're into vintage/aging gear which I am. Next item on the list - a half-inch tape 8-track

. I have my eye on a tascam 38, or even better, a TSR-8

.

DmitryK · Post by **DmitryK** » Tue Oct 10, 2006 12:59 am

I've just installed a new chip instead of the silent one (#2), and it works fine.

Instead of desoldering the chip like everyone seemed to suggest, though, I just broke it off, and then desoldered the pins left on the board. I mean, what's the point if it's going into the garbage bin anyway? It's much easier to solder the pins out, and then clean the holes with a disoldering braid than it is to try and get rid of solder while the chip is in the PCB.

While testing the new chip, the older loud one (#5; the one that caused this thread to be started) suddenly went from loud to almost silent. Thank God! I was afraid it might be something else with the circuit.. Already ordered another replacement..

Thanks to everyone who replied!

DmitryK · Post by **DmitryK** » Wed Oct 11, 2006 8:17 am

For others who need help with the same issue, or just for a small chuckle I put together a small guide:

http://earpick.blogspot.com/

Going to update it with pictures within the next few hours.